Method of processing valve mechanism

ABSTRACT

A method of processing a valve mechanism which includes a valve body having a shut-off surface in the form of a convex spherical surface, a valve hole, a valve seat formed by an opening of the valve hole, and a spring which urges the valve body toward the valve seat, wherein the valve mechanism is so formed that the valve body resists the urging force of the spring in accordance with the pressure increase in the valve hole to be separate from the valve seat, includes the steps of: preparing a processing tool having a processing surface in the form of a convex spherical surface which has the same curvature radius as the shut-off surface of the valve body; positioning the processing tool to the valve seat; and forming the valve seat along the form of the processing surface by pushing the processing surface of the processing tool against the valve seat.

BACKGROUND OF THE INVENTION

The present invention relates to a valve mechanism formed by adifferential pressure regulating valve, for example, for use in arefrigerating circuit for an air conditioner.

The refrigerating circuit for the air conditioner has used at variousportions thereof valve mechanisms formed by the differential pressureregulating valves in order to adjust various pressures in therefrigerating circuit. A valve mechanism disclosed in JapaneseUnexamined Patent Publication No. 11-324909 relieves the pressure in acrank chamber of a refrigerant compressor which forms a refrigeratingcircuit to a low-pressure region in the refrigerating circuit when thepressure becomes extraordinarily high.

Specifically, the valve mechanism includes a spherical valve body, avalve hole in communication with the crank chamber, a valve seat formedby the opening of the valve hole, and a spring which urges the valvebody toward the valve seat. When the pressure in the crank chamberbecomes extraordinarily high, force applied to the valve body in a valveopening direction increases in accordance with the pressure in the valvehole. Therefore, the valve body is separated from the valve seat so asto resist the urging force of the spring, thereby relieving the pressurein the crank chamber to a low-pressure region through the valve hole andan opening between the valve body and the valve seat.

As a valve mechanism for use in the refrigerating circuit, in additionto the valve mechanism which prevents the pressure in the crank chamberof the aforementioned refrigerant compressor from becomingextraordinarily high, a valve mechanism (a relief valve) which relievesextraordinarily high pressure of a high-pressure region in arefrigerating circuit to the atmosphere is mentioned. The valvemechanism which is used as a relief valve may have a structure similarto the valve mechanism, which prevents the pressure in the crank chamberof the refrigerant compressor from becoming extraordinarily high.

However, the valve mechanism is formed so that the valve body is urgedtoward the valve seat by the urging force of the spring. Therefore,under the circumstances where the differential pressure is not appliedto the valve body, for example, when the valve mechanism is assembled,the valve body is urged against the valve seat with relatively largeforce by the urging force of the spring. In addition, the sphericalvalve body is in contact with the valve seat in a sort of angled state.Therefore, the valve body is pushed against the valve seat withrelatively large force, thereby plastically deforming the valve seatalong the form of a part of the outer surface (the spherical surface) ofthe valve body.

When the valve mechanism is assembled, no attention is paid to it thatthe valve body which is directly held, is contacted with the valve seatin a suitable position. Therefore, a contacting position of the valvebody with the valve seat may deviate from the suitable position. Whenthe valve body is pushed against the valve seat in the state of beingdeviated from the suitable position and the valve seat is plasticallydeformed, accordingly, the valve hole cannot be securely shut off by thevalve body which is stabilized in such a state that the valve bodycontacts the valve seat along the form of the plastic deformation.Therefore, even if the pressure in the valve hole is not extraordinarilyhigh, there is a problem that a refrigerant gas leaks from the valvehole to a valve chamber through the opening between valve body and thevalve seat, thereby causing deterioration of the performance of therefrigerating circuit.

In particular, the valve mechanism, which is used as the relief valve,requires the spring which pushes the valve body against the valve seatso as to resist relatively large pressure differential between thehigh-pressure region in the refrigerating circuit and the atmosphere.That is, the spring requires relatively large urging force, for example,compared to the valve mechanism, which prevents the pressure in thecrank chamber of the refrigerant compressor from becomingextraordinarily high. Therefore, when the relief valve is assembled, thevalve body is pushed against the valve seat with further large force byrelatively large urging force of the spring, thereby easily plasticallydeforming the valve seat.

This problem gets further serious in a case where the refrigeratingcircuit uses a carbon dioxide as a refrigerant, for in a case where thecarbon dioxide is used as the refrigerant the high-pressure region inthe refrigerating circuit becomes further high pressure in comparisonwith a case that a chlorofluorocarbon is used as the refrigerant,thereby requiring the spring which has further large urging force.

SUMMARY OF THE INVENTION

The present invention is directed to a method of processing a valvemechanism in which a valve body in contact with a valve seat securelycloses a valve hole.

The present invention produces a method of processing a valve mechanismwhich includes a valve body having a shut-off surface in the form of aconvex spherical surface, a valve hole whose opening degree is adjustedby the valve body, a valve seat formed by an opening of the valve hole,and a spring which urges the valve body toward the valve seat. The valvemechanism is so formed that the valve body resists the urging force ofthe spring in accordance with the pressure increase in the valve hole tobe separate from the valve seat. The method includes the steps of:preparing a processing tool having a processing surface in the form of aconvex spherical surface which has the same curvature radius as theshut-off surface of the valve body; positioning the processing tool tothe valve seat; and forming the valve seat along the form of theprocessing surface by pushing the processing surface of the processingtool against the valve seat.

The present invention also produces a tool for processing a valve seatbeing used upon processing a valve mechanism which includes a valve bodyhaving a shut-off surface in the form of a convex spherical surface, avalve hole whose opening degree is adjusted by the valve body, the valveseat formed by an opening of the valve hole, and a spring which urgesthe valve body toward the valve seat. The valve mechanism is so formedthat the valve body resists the urging force of the spring in accordancewith the pressure increase in the valve hole to be separate from thevalve seat. The processing tool includes a processing surface in theform of a convex spherical surface having the same curvature radius asthe shut-off surface of the valve body.

Other aspects and advantages of the invention will become apparent fromthe following description, taken in conjunction with the accompanyingdrawings, illustrating by way of example the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel areset forth with particularity in the appended claims. The invention,together with objects and advantages thereof, may best be understood byreference to the following description of the presently preferredembodiments, together with the accompanying drawing, in which:

FIG. 1 is a longitudinal sectional view showing a relief valve;

FIG. 2 is a diagram illustrating a process for producing the reliefvalve; and

FIG. 3 is a diagram illustrating a process for producing another reliefvalve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A method of processing a valve mechanism according to a preferredembodiment of the present invention will now be described below. Thepresent preferred embodiment is embodied in a method of processing arelief valve for use in a refrigerating circuit of an air conditionerfunctioning as a fluid circuit.

First of all, the refrigerating circuit for the air conditioner will bedescribed. As shown in FIG. 1, a refrigerating circuit 51 includes arefrigerant compressor 52, a gas cooler 53, an expansion valve 54 and anevaporator 55. The refrigerant compressor 52 also includes a suctionchamber 52 a, a compression chamber 52 b, a discharge chamber 52 c and acompressor housing 52 d. The refrigerant compressor 52 introduces arefrigerant gas from the suction chamber 52 a into the compressionchamber 52 b, compresses the introduced refrigerant gas therein, anddischarges the compressed refrigerant gas into the discharge chamber 52c. The gas cooler 53 cools down the refrigerant gas of high pressurefrom the discharge chamber 52 c of the refrigerant compressor 52. Theexpansion valve 54 throttles the refrigerant gas from the gas cooler 53.The evaporator 55 evaporates the refrigerant gas from the expansionvalve 54. A carbon dioxide is used as the refrigerant gas in therefrigerating circuit 51. The refrigerant compressor 52 is equipped witha relief valve 10.

A structure of the relief valve 10 will now be described. Stillreferring to FIG. 1, the relief valve 10 has a valve housing 11 whichforms a configuration thereof. The valve housing 11 includes a firstbody 12 and a second body 13. The first body 12 is screwed into thecompressor housing 52 d of the refrigerant compressor 52. The secondbody 13 is screwed onto the first body 12 while arranged outside thecompressor housing 52 d. The first body 12 has a partitioning portion 14which is screwed into the second body 13. The partitioning portion 14 ofthe first body 12 and the second body 13 define a valve chamber 15. Thepartitioning portion 14 separates the valve chamber 15 from thedischarge chamber 52 c which is defined in the compressor housing 52 dof the refrigerant compressor 52. The partitioning portion 14 has an endface 14 a which faces the valve chamber 15. The end face 14 a has a flatshape.

The first body 12 has formed therethrough a communication hole 16 whichextends in a direction perpendicular to the end face 14 a of thepartitioning portion 14. The communication hole 16 interconnects thevalve chamber 15 and the discharge chamber 52 c. The discharge chamber52 c is regarded as a high-pressure region in the refrigerating circuit51. The second body 13 has a circular wall which surrounds the valvechamber 15, and the circular wall has formed a plurality of ports 13 awhich radially extends therethrough. The valve chamber 15 is opened tothe atmosphere through the ports 13 a. That is, the discharge chamber 52c of the refrigerant compressor 52 and the atmosphere are incommunication via the communication hole 16, the valve chamber 15 andthe ports 13 a.

The valve chamber 15 has accommodated therein a valve body 18 which isformed by a spherical body made of steel. The valve body 18 is movablewith respect to the end face 14 of the partitioning portion 14 in adirection in which the valve body 18 is contacted with or separated fromthe partitioning portion 14. The valve chamber 15 also has accommodatedtherein a spring seat 19, which is movable in the valve chamber 15. Thespring seat 19 has a seating face 19 a in the form of a conical hollowsurface on the side of the end face 14 a of the partitioning portion 14.The seating face 19 a of the seat spring 19 is contacted with the valvebody 18. The valve chamber 15 further has accommodated therein a spring21 made of a coil spring. The spring seat 19 is located on the oppositeside to the partitioning portion 14 in the valve chamber 15 andsupported through the spring 21 by the second body 13. The spring 21urges the valve body 18 toward the end face 14 a of the partitioningportion 14 through the spring seat 19.

The end of the communication hole 16 located on the side of the valvechamber 15 is opened on the end face 14 a of the partitioning portion14. In a state where the valve body 18 contacts the end face 14 a of thepartitioning portion 14, a part of the outer surface (spherical surface)of the valve body 18, in other words, a shut-off surface 18 a in theform of a convex spherical surface is contacted with the opening of thecommunication hole 16 in a circular region, thereby shutting off thecommunication between the communication hole 16 and the valve chamber15. That is, the communication hole 16 forms a valve hole, and theopening of the communication hole 16, which is formed on the end face 14a of the partitioning portion 14, forms a valve seat 24. The valve seat24 is plated with a material such as tin, thereby relaxing a plasticdeformation caused by the contact with the valve body 18. Consequently,a sealing performance between the valve seat 24 and the valve body 18 isimproved.

In a case where the pressure in the discharge chamber 52 c of therefrigerant compressor 52 is not extraordinarily high, the force appliedto the valve body 18 in a valve opening direction (upward in FIG. 1)becomes small in accordance with the pressure in the communication hole16. In this case, since the urging force of the spring 21 roughlycontrols the position of the valve body 18, the valve body 18 is incontact with the valve seat 24. Therefore, the valve body 18 shuts offthe communication between the communication hole 16 and the valvechamber 15, thereby preventing the refrigerant gas in the dischargechamber 52 c from being released into the atmosphere.

From this state, if the pressure in the discharge chamber 52 c is aboutto rise extraordinarily high for any reason, the force applied to thevalve body 18 in the valve opening direction (upward in FIG. 1) becomesexcessive in accordance with the pressure in the communication hole 16.Therefore, the valve body 18 is moved against the urging force of thespring 21 so as to be separate from the seat valve 24. When thecommunication hole 16 is connected to the valve chamber 15 by themovement of the valve body 18, the refrigerant gas in the dischargechamber 52 c is released into the atmosphere through the communicationhole 16, the valve chamber 15 and the ports 13 a, thereby preventing thepressure in the discharge chamber 52 c from extraordinarily rising.

The pressure in the discharge chamber 52 c at the time when the valvebody 18 starts to be separate from the valve seat 24, in other words,the pressure in the discharge chamber 52 c upon opening the relief valve10, is set by adjusting the thickness of a shim 26 interposed betweenthe first body 12 and the second body 13. That is, by adjusting thethickness of the shim 26, not only a screwing amount of the first body12 (the partitioning portion 14) to the second body 13 but also thestrength of the urging force of the spring 21, which is applied to thevalve body 18 in contact with the valve seat 24, is adjusted.

A method of processing the relief valve 10 will now be described.Referring to FIG. 2, the first body 12, where the second body 13 of FIG.1 has not been screwed, is shown. In this state, a processing tool 31which includes the valve body 18 and a tool 32 for holding the valvebody 18 is prepared. The processing tool 31 is positioned to the valveseat 24 so that a center point S of the valve body 18 locates on acentral axis L of the communication hole 16 including the center of thevalve seat 24.

In this positioned state, the processing tool 31 and the valve seat 24are relatively moved by an operation of a processing machine (not shown)in a direction in which the processing tool 31 and the valve seat 24approach each other. Therefore, the shut-off valve 18 a of the valvebody 18 which the holding tool 32 holds, that is, a processing surfacein the form of a convex spherical surface provided with the processingtool 31, which has the same curvature radius as the shut-off surface 18a of the valve body 18, is pushed against the valve seat 24. The forceof the processing machine that pushes the valve body 18 against thevalve seat 24 through the holding tool 32 is set so as to have the valuemore than that of the spring 21 that pushes the valve body 18 againstthe valve seat 24 through the spring seat 19, for example, under thecircumstances where the pressure differential between the pressure inthe discharge chamber 52 c and the atmosphere is not applied to thevalve body 18. By thus pushing the valve body 18 of the processing tool31 against the valve seat 24, the shape of the valve seat 24 is formedor plastically deformed from a circular line (whose cross sectional viewis shown by chain double-dashed line in an enlarged circle A of FIG. 2)to a three-dimensional shape along a part of the shut-off surface 18 aof the valve body 18.

It is noted that the process in which the valve seat 24 is plated isperformed after the above-mentioned process in which the valve seat 24is formed by the processing tool 31. This processing order prevents theplating not only from hindering the formation of the valve seat 24 bythe processing tool 31 but also from being damaged by the pushing forceof the processing tool 31.

The above-mentioned preferred embodiment has the following advantageouseffects.

(1) The valve seat 24 is previously plastically deformed into itssuitable state by the processing tool 31 so as not to be plasticallydeformed in a state that a contacting position of the valve body 18 withthe valve seat 24 is deviated from the suitable position. Therefore, thecommunication hole 16 of the relief valve 10 is securely blocked by thevalve body 18 which contacts the valve seat 24 along the form of theplastic deformation, thereby preventing the refrigerant gas from leakingfrom the discharge chamber 52 c to the atmosphere in a state that thepressure in the discharge chamber 52 c is not extraordinarily high, andimproving the performance of the refrigerating circuit 51, accordingly.

(2) The valve body 18 is used for the processing tool 31. By thusforming the valve seat 24 with the actual valve body 18 for use in therelief valve 10, the formation is suitably performed.

(3) In order to push the valve body 18 against the valve seat 24 so asto resist a relatively large pressure differential between the insideand the outside of the refrigerating circuit 51, the relief valve 10requires the spring 21 whose urging force is relatively large.Heretofore, the valve seat 24 was easily plastically deformed into itsunsuitable state by pushing the valve body 18 against the valve seat 24with a relatively large force. The present embodiment of the presentinvention is particularly effective to be embodied in the method ofprocessing the relief valve 10.

(4) Since in a case where a carbon dioxide is used as a refrigerant inthe refrigerating circuit 51, a high-pressure region (discharge chamber52 c) in the refrigerating circuit 51 becomes extraordinarily highpressure, for example, in comparison with a case where achlorofluorocarbon is used as the refrigerant in the refrigeratingcircuit 51, a spring 21 whose urging force is further large is needed.Therefore, in the prior art, the valve body 18 was pushed against thevalve seat 24 further strongly and the valve seat 24 was easilyplastically deformed into its unsuitable state, accordingly. That is,the present invention is particularly effective to be embodied in amethod of processing the relief valve 10 provided in the refrigeratingcircuit 51 which uses carbon dioxide.

The present invention is modified within the scope of the appendedclaims, as exemplified below.

As shown in FIG. 3, when the relief valve 10 is processed, a member thatis different from the valve body 18 may be used as a processing tool 41for forming the valve seat 24. The processing tool 41 of FIG. 3 has arod-like shape and has on the end of the rod-like shape a processingsurface 41 a which forms a hemispherical surface functioning as a convexspherical surface. The processing surface 41 a of the processing tool 41has the same curvature radius as the shut-off surface 18 a of the valvebody 18. The processing tool 41 is pushed against the valve seat 24through the processing surface 41 a, thereby forming the valve seat 24.

In the above-modified embodiment, the different member from the valvebody 18 is used as the processing tool 41. That is, the different memberfrom the valve body 18 is used exclusively as the processing surface 41a of the processing tool 41. By providing the processing tool 41 withthe exclusive processing surface 41 a, the valve seat 24 is efficientlyformed. This technique is suitable for the mass production of the reliefvalve 10. Such an effect is accomplished even by modifying theabove-preferred embodiment so as to replace the valve body 18 of theprocessing tool 31 by a spherical body used exclusively for forming.

In the above-preferred embodiment, the relief valve 10 has used thespherical body (a ball valve) as the valve body 18. However, the valvebody 18 of the relief valve 10 is not limited to the spherical body ifit has the shut-off surface in the form of convex spherical surface. Ahemispherical body may be used as the valve body 18. That is, theprocessing method according to the present invention may be adapted forthe valve mechanism using the valve body other than the valve body inthe form of spherical body.

In the above-preferred embodiment, the relief valve 10 has used the coilspring as the spring 21. However, the spring 21 of the relief valve 10is not limited to the coil spring. A leaf spring may be used as thespring 21. That is, the processing method according to the presentinvention may be adapted for the valve mechanism using the spring otherthan the coil spring.

In the above-preferred embodiment, the present invention is embodied inthe method of processing the relief valve 10. In a modified embodimentto the preferred embodiment, the present invention is embodied in amethod of processing a valve mechanism which relieves the pressure in acrank chamber of the refrigerant compressor 52 to a low-pressure regionin the refrigerating circuit 51 when the pressure becomesextraordinarily high.

The present invention is not limited to be embodied in a method ofprocessing a valve mechanism provided with a refrigerating circuit whichuses a carbon dioxide as a refrigerant, but may be embodied in a methodof processing a valve mechanism provided with a refrigerating circuitwhich uses a chlorofluorocarbon as the refrigerant.

The present invention is not limited to be embodied in the method ofprocessing the valve mechanism provided with the refrigerating circuit,but may be embodied in a method of processing a valve mechanism providedwith an air circuit or a hydraulic circuit.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein but may be modified.

1. A method of processing a valve mechanism which includes a valve bodyhaving a shut-off surface in the form of a convex spherical surface, avalve hole whose opening degree is adjusted by the valve body, a valveseat formed by an opening of the valve hole, and a spring which urgesthe valve body toward the valve seat, the valve mechanism being soformed that the valve body resists the urging force of the spring inaccordance with the pressure increase in the valve hole to be separatefrom the valve seat, the method comprising the steps of: preparing aprocessing tool having a processing surface in the form of a convexspherical surface which has the same curvature radius as the shut-offsurface of the valve body; positioning the processing tool to the valveseat; and forming the valve seat along the form of the processingsurface by pushing the processing surface of the processing tool againstthe valve seat.
 2. The method according to claim 1, wherein the valvebody is used for the processing tool.
 3. The method according to claim1, wherein a member different from the valve body is used for theprocessing tool.
 4. The method according to claim 1, wherein the valvemechanism is a relief valve for use in a hydraulic circuit.
 5. Themethod according to claim 4, wherein the hydraulic circuit is arefrigerating circuit for an air conditioner, the refrigerating circuitusing a carbon dioxide as a refrigerant.
 6. The method according toclaim 1, wherein the force that pushes the processing tool against thevalve seat is set so as to have the value more than that of the springthat pushes the valve body against the valve seat, under thecircumstances where pressure differential is not applied to the valvebody.
 7. The method according to claim 1, further comprising the stepof: plating the valve seat after the forming process of the valve seat.8. A tool for processing a valve seat being used upon processing a valvemechanism which includes a valve body having a shut-off surface in theform of a convex spherical surface, a valve hole whose opening degree isadjusted by the valve body, the valve seat formed by an opening of thevalve hole, and a spring which urges the valve body toward the valveseat, the valve mechanism being so formed that the valve body resiststhe urging force of the spring in accordance with the pressure increasein the valve hole to be separate from the valve seat, comprising: aprocessing surface in the form of a convex spherical surface having thesame curvature radius as the shut-off surface of the valve body.
 9. Theprocessing tool according to claim 8, wherein the processing surface ofthe processing tool is the shut-off surface of the valve body.